The development of self-contained breathing systems has enabled humans to dive and remain underwater for several hours. The ability to remain underwater for an extended period of time can enable divers to reach considerable depths and cover expansive distances in exploring underwater terrain.
A problem commonly encountered by divers is an inability to accurately locate position underwater. Position is typically expressed in terms of three co-ordinates. The position of a diver underwater can be expressed in terms of a latitude, a longitude, and a depth co-ordinate. The latitude and the longitude co-ordinates represent the latitude and the longitude of a point on the surface of the water directly above the diver. The depth co-ordinate represents the depth of the diver below the surface of the water. A dive computer similar to a ProPlus 2 manufactured by Oceanic Worldwide of San Leandro, Calif. can be used to track depth during a dive.